Field of the Invention
The present invention relates to a light scanning apparatus which includes a light intensity controller configured to control the light intensity of a light beam, and to an image forming apparatus.
Description of the Related Art
Some known a light scanning apparatus provided in an image forming apparatus uses a method of irradiating a photosensitive drum via an fθ lens with a light beam which is deflected by a rotary polygon mirror after exiting a light source. In recent years, an image forming apparatus has been demanded to form a high quality image at high speed and, to meet the demand, uses a multi-beam light source, which is configured to emit a plurality of light beams concurrently from a plurality of light emitting points, as a light source for emitting light beams.
Meanwhile, a light scanning apparatus switches the rotation speed of the rotary polygon mirror and the number of light emitting points of the light source in response to a change in printing speed (transmission), a change in image resolution, or a change in the rotation speed of the photosensitive drum which depends on the thickness of the recording medium. In U.S. Pat. No. 8,305,416, there is disclosed a light intensity control under which light for an image forming area on a surface of the photosensitive drum is emitted from a smaller number of light emitting points that is suited to image data, and light for a non-image forming area on the drum surface is emitted from all light emitting points on light emission schedules different from one another.
However, in the case where the number of light beams is changeovered by using laser drive substrates of the same type in which control for supplying a bias current to a plurality of light emitting points is exerted in order to improve the light beam output responsiveness for different types of light scanning apparatus, a bias current is supplied also to a light emitting point that is not in use. This presents a difficulty in reducing the power consumption of the light scanning apparatus. When the light source used is a VCSEL or another light source that emits a large number of light beams, power consumption due to the current supplied to light emitting points that are not in use is particularly large, which is a problem.